The present invention is related to system and methods for fire safety, and more particularly to a system and method for fire control during and after earthquakes.
Damage from earthquakes arises not only due to the seismic activity itself but also due to the effects of that initial damage. In fact, studies have shown that damage and devastation from earthquakes are often as much due to secondary factors (such as fire, flood and electrical shock) as due to the original seismic disturbance itself. Attention has gradually turned to these secondary factors and to methods of minimizing their effect in the event of an earthquake.
The Japanese have been leaders in the area of analyzing the occurrence of electrical fire in the wake of a seismic disturbance. Studies such as xe2x80x9cInvestigation Reports and Igniting Experiments on the Electrical Causes of Fires Started after the Earthquake in Kobe Areaxe2x80x941995xe2x80x9d make direct links between electrical fires and earthquakes, and use specific earthquake data as part of the research base.
Electrical fires occur most frequently when external power disrupted by the seismic even is once again restored. One reason for such fires is that electrical power is oftentimes being supplied to wiring systems damaged by the seismic disturbance.
Hogan (U.S. Pat. No. 4,414,994) notes this problem and suggests a solution. According to Hogan, a safety system can be built which detects earthquakes having a magnitude greater than a preset value and which, upon such detection, instantly shuts off electricity, gas and water supplies to a building. The safety system includes a housing containing a normally-open electrical contractor connected between the electric service entrance and the distribution circuit breaker panel. When seismic activity of sufficient magnitude is detected, the normally-open electrical contractor opens, removing power from the circuit breaker panel.
Hogan states that normally-closed solenoid valves can be placed in the gas and water pipelines. The solenoid valves are connected to breakers in the circuit breaker panel such that when power to the breaker panel is cut off, the solenoid valves close, cutting off the water and gas supplied to the building.
The approach described by Hogan is effective in shutting off water, gas and electricity to a building on the occurrence of seismic activity. Any shock of sufficient magnitude will also, however, trigger a shut down. In addition, Hogan""s design will shut off water, gas and electricity to a building on occurrence not only of seismic activity but also when electrical power is cut for any reason (e.g., lightning or downed power lines). This design aspect makes the system less useful in a number of household and business applications.
What is needed is a system and method of disabling utilities to a building both during and after an earthquake.
According to one aspect of the present invention, a system and method of disabling utility service supplied to a building during and after an earthquake is described. A shock sensor for sensing seismic activity is provided and a seismic activity threshold is established. Seismic activity is sensed over time and the seismic activity sensed is compared to the seismic activity threshold. When seismic activity exceeds the seismic activity threshold, utility service is cut off to the building.